Evaporative heat exchanger



1965 J. ENGALlTCHEFF, JR., ETAL 3,169,575

EVAPORATIVE HEAT EXCHANGER Filed Oct. 27, 1961 6 Sheets-Sheet 1REFRIGERANT m AIR DISCHARGE L 26 21 w t f I 1 )f' i I I l6 INVENTORSJohn Engolitcheff, Jr.,

Thomas F. Facius TTORNEY' Feb. 16, 1965 J. ENGALlTCHEFF, JR., ETALEVAPORATIVE HEAT EXCHANGER Filed Oct. 27, 1961 AIR DISCHARGE 6Sheets-Sheet 2 T WATER iii? il FLT? l W J.

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MAKE-1 INVENTORS John Engulitcheff, Jr.,

Thomas F. Facius ATTORNEYS Feb. 16, 1965 J. ENGALITCHEFF, JR, ETAL.3,169,575

EVAPORATIVE HEAT EXCHANGER 6 Sheets-Sheet 3 Filed Oct. 27, 1961 is E235:; z;

INVENTORS John Engaliic'neffldn,

Thomas F. Fqcius Feb. 16, 1965 Filed Oct. 27, 1961 TEMPERATURE J.ENGALITCHEFF, JR., ETAL 3,16

EVAPORATIVE HEAT EXCHANGER 6 Sheets-Sheet 4 'Zl- REFRIGERANT REFRIGERANTCONDENSING B SUPERHEAT REMOVAL sus-coouuc AND SOME CONDENSING 0F REFRIG.IN EXTERNAL HEAT EXCHANGER \HEATED SPRAY wATER SPRAY WATER FROM EXTERNALHEAT KM/ EXCHANGER AIR INVENTORS John Engalitcheff, Jr.,

Thomas F. Fucius BY m,fiw,w m TTORNEYTS 1965 J. ENGALITCHEFF, JR., ETAL3,169,575

EVAPORATIVE HEAT EXCHANGER Filed Oct. 27, 1961 6 Sheets-Sheet 5 SPRAY JCHAMBER I COIL SECTION AIR INVENTORS John Engoli'rcheff, Jr., Thomas F.Fucius AIRIN ATTORNEYS Feb. 16, 1965 J. ENGALITCHEFF, JR., ETAL3,169,575

EVAPORATIVE HEAT EXCHANGER Filed Oct. 27, 1961 6 Sheets-Sheet 6 SPRAYFROM CHAMBER TUBE-40o COILSECTION J4} I LIQUIDIN ANNULAR SPRAY WATER mINNER PIPE TEMPERATURE INVENTORS John Engolitcheff, Jr. Thomas F. Fqciusagww fiw mgm ATTORNEYS United States Patent EVAPDRATIVE I-EAT EXCHANGERJohn Engalitchefi, Jr., Gibson Island, and Thomas F. Facials, Baltimore,Md, assignors to Baltimore Aircoil Company, Inc, Baltimore, Md., acorporation of Maryland Filed Oct. 27, 1961, Ser. No. 148,254

7 Claims. (Cl. 1651) This invention relates to evaporative' heatexchangers and more particularly to methods and apparatus for extractingheat from fluids in operations such as the condensing of refrigerantsand/ or the cooling of liquids.

In an evaporative condenser, the fluid from which heat is sought to beextracted is circulated through a coil or tube bank which is disposed ina chamber which has a water reservoir or sump at its bottom. Theapparatus is provided with means for flowing air upwardly around thecoil while water from the sump is pumped to the top of the tank andsprayed downwardly from a spray tree in droplets which fallcountercurre'nt to the air flowing over the coil. The air circulatingcounter to the droplets causes a measure of evaporation of the water andthe latent heat necessary to support this evaporation is taken from thefluid in the coils.

Now, in a system of the type described above, the spray water leavingthe spray tree and before it begins to contact the coil sectioncontaining the fluid from which heat is to be extracted, is cooler thanthe air which has been moving upwardly through the coils to causeevaporation; Accordingly between the spray tree and the beginning of thecoil section, the air which is leaving the f of water.

tures of the spray water and the air that the spray moving down to thecoil section "will be cooled by the counterfiowing air leaving thesystem rather than/taking up heat from that air. 7

it is an object of the present invention to provide an evaporativecondenser or other, heat exchanger of improved thermal efiiciency whichis characterized by the capability of maintaining an appreciabletemperature dif-' ference between the flowing water spray andcounteriiowing air in'the region between the spray header and thecoil. jThe present invention olfersthe advantage that by its use the heatextracting capacity of [an evaporativeconi denser or heat exchanger ofany given size is increased so thatif the present inventionis appliedtoan existing installation it will increase its cooling capacity] Ofcourse, if the same cooling capacity is desired then, with the presentinvention, it can be achieved with smaller equipment. a

Other objects and advantages of this invention will be I apparent uponconsideration of the following detailed description of severalembodiments thereof in conjunction with the annexed drawings wherein:

FIGURE 1 is a schematic yiew in vertical sectionof an evaporativecondenser constructed in accordance with the principles of the presentinvention to incorporate aheat exchanger through which the spray waterpasses and. is

preheated on its way to the spray head, the heat 'exchang or beingphysically separate from the condenser casing; FIGURE 2 is a view invertical section, showing'a It is proposed according to the presentinvention .to 4

eliminate this waste and so to adjust the relative tempera-' ice in thevarious regions of a sytsem such as that shown in FIGURE 1;

FIGURE 5 is a view similar in that of FIGURE 4,

but showing relative temperatures of the heat exchange media in variouszones of a in FIGURE 2;

FIGURE 6 is a view similar to FIGURE 3, but represystem such as thatshown 'senting the relative temperature curves of air, spray water,

and fluid to have heat extracted therefrom where the coil containsaliquid which is being cooled by the extraction of sensible heat asdistinct from latent heat;

FIGURE 7 is a graphic representation ofthe relative temperature of air,spray water and liquid to be cooled under conditions which would prevailif the apparatus of FIGURE 1 were used to cool a liquid rather than tocondense a refrigerant gas; and g p FIGURE 8 is a view similar to FIGURE7 but showing the relative temperature curves for air, spray water and aliquid to be cooled as these would be iri the various zones in theapparatus of FIGURE 2 if'that apparatus a were'used to cool aliquidrather thanto con-dense a "refrigerant.

casing 10 there is provided'a reservoir or sump 11 for.

spray water, and reservoir is maintained at a predetermined level bymakeup water supplied by a conduit 12 througha float valve 13 ofconventional construction controlled by, a float l4. Waterfrom thereservoir. 11 is withdrawn by a pump 15 through a conduit 16 anddelivered-through a conduit 17 to a heat exchanger diagrammaticallyindicated at 18. The cooling water is one phase a conduit 21, gives upsome'of its heat'to the spray water, and leaves through conduit 22 fromwhich it is delivered to the coils v23 inthe casing 10. ;The condensedrefrigerant leaves the-condenser through conduit 24. The

refrigerant .is only partly cooled in heatexchanger l3, but theprincipal condensing of the sanie'takes place: in

the coils 23. To this end, the cooling water is sprayed over the coils23 in droplet form and the water'tempera .ture is kept low byevaporation induced by air flowcaused by a fan 25 which pumpsair'vertically upwardly through the casing 10 countercurrent to thespray'water which is falling by gravity. -Drift eliminators 26 catch thewater in the air which leaving the system and return it to the system.

Above and below the coils'23'there are located wet dech sections 26 and27. These wet decksections are merely groups of corrugated metal sheetsdisposed in mutually parallel relation in such a way as toicollectwater. on

their surfaces' for evaporation by the, air passing ithere across. This,of course has the'fefiect of cooling the' water droplets flowing to andflowing from the coils 23. a

' its own air exhaust duct In FIGURES 3 and 4 there are set forth curvesrepresenting relative temperature changes which occur in evaporativeheat exchangers; The curves of FIGURE 3 represent the conventional heatexchanger while those of FIGURE 4 represent the heat exchanger of thepresent invention. In FIGURE 3 there is diagrammatically represented aspray tree 30, a coil section 31, a sump 32 and a fan 33. In actualstructures these are arranged vertically, but in FIGURE 3 they arediagrammed horizontally to correlate the apparatus with the temperaturecurves.

The abscissa of these curves represent position in the system, while theordinates represent temperaturerising in the direction of the arrow. Therefrigerant entering the top of a conventional system contains somesuperheat. This is extracted in the upper part of the coil section.Thereafter, heat of vaporization is extracted as the refrigerant changesfrom gaseous to liquid phase, and then, at thevery bottom of the coilsection 31, a small amount of sub-cooling occurs.

Nowin FIGURE 3 where there is no heat exchanger such as heatexchangerlti, the air enteringthe spray chamber zone is the hottest airin the entire system, see the right side of FIGURE 3. The water is atabout the temperature prevailingin the reservoir32, and it has beenfound that this temperature is regularly and appreciably below thetemperature of air leaving the uppermost pass of the coils 31.Obviously, if the air is warmer than the water, the water will cool theair and then this air will be forthwith vented to atmosphere. 1 Asidefrom this waste, the temperature difference between air and spray waterdoes not get to a desired level until the spray water has progressed afair distance into the coil system.

On the other hand with applicants improvement the spray water is not ledfrom the reservoir directly to the spray head 20, but instead is firstpassed through the heat exchanger 18. The effect of this is set forth inFIGURE 4 which is a diagram made in the same fashion as FIG- URE 3 toshow graphically the advantage of the construction of FIGURE 1 overthe'prior art the function of which is set out in FIGURE 3. In FIGURE 4the parts which appear diagrammatically bear the reference numerals ofthe equivalent parts in FIGURE 1. paring FIGURES 3 and 4 the advantageof passing the cooling water through the heat exchanger 18 on its way tothe spray tree is graphically apparent. Note that the spray Water inpassing through heat exchanger 18 has its temperature raised from levelA to level B, see FIGURE 4, so that the water entering the spray'tree 20is much warmer than' the air leaving the casing 10, with the result.that the entering Water is cooled and the leaving aircon- 4 As shown inFIGURE 4 condensation may commence in the heat exchanger 13.

In FIGURE 1 the achievement of the rise in temperature of the coolingwater before its entry into the spray trees 20 is accomplished'by a heatexchanger which is physically separate from the evaporative condensercasing. In FIGURE 2 there is shown a ve-ry-eflicient arrangement whereinthe preheating of the cooled water is accomplished first by flowing itcountercurrent to the refrigerant as the inside phase of a dual heatexchanger, the outside phase of which is between the refrigerant and thespray of cooling water from the spray trees.

In FIGURE 2 the evaporative heat exchanger casing is defined by numeral33; A fan 34 is provided to pump air substantially vertically throughthe casing from bottom to top. At the bottom of the tower there is awater reservoir or sump 35 provided with a fioat operated make-up valvegenerally designated at 36. Cooling water is withdrawn from the sump 35through a pipe 37 leading to the intake of a pump 38. The pump 38delivers the water through a conduit 29 which enters the inner tube 49aof concentric tube heat exchange coil 40 through a suitable end fitting41. Through a similar end fitting 42 the cooling water leaves the coil4%) and is delivered by a pipe 43 to spray tree 44. The coils 49 are fedwith refrigerant through a conduit 45 leading to the outer tube 4% ofthe coil 43. The refrigerant is withdrawn through a conduit 46; Therefrigerant circulates in an annular zone through the coil4tisurrounding the tube 40a which contains the coolant water, the outersurface of the refrigerant tube 49b being exposed to'the coolingdroplets of water issuingfrom the spray trees 44. It will be noted thatthe water is flowing upwardly through the coil 49a I counter to thedownward flow of the refrigerant to be condensed in tube 4%. On theother hand, the spray issuing from the spray trees 44 is. flowinggenerally'concurrently with the refrigerant to be condensed wh-ileboththe spray and the liquid to be cooled are flowing countercurrently tothe air. Drift eliminators 47 similar in structure and function toeliminators 26 are provided at the top of the casing 33. Wet decksections 43 and 49 are provided, section 48 being between the spraytrees 44 and the coil 40, and section 49 being between the coil 46 andthe sump 35; Thesesections 43 and 49 correspond respectively instructure and function to sections 26 and 27 shown in FIGURE 1. 1

The effect of these wet deck sections is to improve the air-watercontact thereby to increase evaporation of the water and to improve theamount of cooling that can be accomplished per unitlength of fall of thecooling water. FIGURE 5 is a diagrammatic illustration in the style ofFIGURE 4 but is prepared to show the relative temperature curves for therefrigerant, the spray water and By com- 7 the air as they move throughthe apparatus of FIGURE 2. The diagrammatic parts of the system ofFIGURE 5 bear the same numbers as have been assigned to those parts inFIGURE 2. The broken line indicates the spray water V tinues to pick upheat with the result that the water at the moment of commencement ofspray is already, and continues to be all the way through the coils 23,much warmer than the air which is cooling it. The increase in thetemperature of the spray water entering the spray chamber would, ofcourse, not result in increased efliciency except for the factthat theheat which causes the rise from its entering temperature as shown inFIGURE 3 to the entering temperature as shown in FIGURE 4 is derivedfrom the material to be cooled, i.e. the refrig-' erant. This materialhas the superheat removed'before it enters coil 23 with the result thatthe amount of condensing per unit of surface of the equipmentisincreased.

in the inner pipe during the preheat operation. Note that it ispreheated from a sump temperature indicated at .A to a spray treetemperature indciated at B and that A is much lower than theairtemperature at C although thethat this superheat is dissipated muchmore rapidly thanin conventional apparatus dueto the fact that therefrigerant is having heat extracted from both the inner and outersurfaces of its annular. path. a

, f Of course, in the condensation of a refrigerant, a temperature curverepresenting heat extraction is a straight linesince there is no changein sensible heat, the extracted heat going to bring about a change instate, i.e., from gas to liquid. Accordingly, the refrigerant curves inFIG- URES 3, 4, and 5 are essentially straight lines. The apparatus ofthe present invention is, however, quite suitable for cooling liquids,i.e., the extraction of sensible heat from a liquid. In FIGURES 6, 7,and 8 there are shown temperature curves quite similar to those shown inFIG- URES 3, 4, and 5 respectively except that the fluid from which heatis extracted is a liquid rather than a gas. The curves of FIGURES 6, 7,and 8, therefore, represent the change in relative temperature whichoccurs in extracting heat from a liquid which stays in liquid phasethroughout the entire passage through the coil section. FIGURE 6represents the prior art evaporative heat exchanger as it deals with thecooling of a liquid. FIGURE 7 represents the apparatus of FIGURE 1 usedfor cooling at liquid or other fluid as distinct from condensing andFIGURE 8 represents the use of the apparatus of FIGURE 2 for coolinginstead of condensing. By studying the temperature curves of thesefigures it can be seen that the advantage of passing the cooling waterin heat exchange relationship to the incoming material from which heatis to be extracted applies regardless of whether the heat is extractedfor the purpose of reducing the sensible heat, i.e., the measurabletemperature of a fluid, or for the purpose of bringing about a change ofstate.

While wet deck sections are shown in both of FIGURES 1 and 2, these areoperational to the system and may be removed if desired. The heating ofthe entering spray water with the entering fluid to have heat extractedfrom it increases the entering temperature of the spray water as shownin FIGURES 4 and 7, and thus establishes a larger than conventionaltemperature difference between the air and the spray water, thistemperature difierence has a counterbalancing effect on the smallertemperature difierence between the fluid in the coil 23 and the spraywater. In this section of the evaporative heat exchanger using theheated spray water from the external heater 18, there is only a smallreduction in capacity as compared to the same section of a conventionalheat exchanger (10%15%). The external heater accounts for additionalcapacity as much as 40%50%. This results in a net gain of approximately35% more capacity than a conventional evaporative heat exchanger. Theuse of the double pipe heat exchanger shown in FIGURE 2 results inadditional capacity as compared to the FIGURE 1 system. In the case ofFIGURE 2, there is a larger temperature difference between the spraywater and the fluid in the annular space. This is because the fluidentering the double pipe coil is at its highest temperature.

What is claimed is:

1. The method of improving the efliciency of evapora tive heatextraction that comprises as the first step in extracting heat from afluid that has absorbed heat, passing said fluid to have heat extractedtherefrom and a cooling liquid in mutual heat exchange relation withoutevaporation of said cooling liquid and then passing the same fluid andof all said liquid in mutual heat exchange relation while evaporating atleast a portion of said cooling liquid.

2. The method of improving the efliciency of evaporative heat extractionthat comprises as the first step in extracting heat from a fluid thathas absorbed heat, passing said fluid to have heat extracted therefromand a cooling liquid in mutual heat exchange relation withoutevaporation of said cooling liquid and then passing the same fluid andof all said liquid in mutual heat exchange relation while evaporating atleast a portion of said cooling liquid by direct contact with acounterflowing air appreciably cooler than said cooling liquid at thebeginning of the contact.

3. The method of improving the efliciency of evaporative cool-ing thatcomprises passing the fluid to have heat extracted therefrom and thecooling liquid in countercurrent flow, indirect heat exchangerelationship and then without introducing additional heat to said liquidpassing said fluid and all of said liquid in concurrent flow, indirectheat exchange relationship while evaporating a portion of the coolingliquid.

4. Apparatus for cooling fluids under conditions of high thermalefliciency that comprises a coil, means to pass the fluid to be cooledinto the top of said coil and to withdraw it from the bottom of saidcoil, means for spraying cooling water downwardly over said coil, meansbelow said coil to collect water, means to cause a flow of air upwardlythrough said coil and counter to said spray and means defining a flowpath from said collecting means to said spray means and means in saidflow path for passing said water in heat exchange relation to said fluidto be cooled before said liquid enters the top of said coil.

5. Apparatus for cooling fluids under conditions of high thermalefliciency that comprises a coil, means to pass the fluid to be cooledinto the top of said coil and to withdraw it from the bottom of saidcoil, means for spraying cooling water downwardly over said coil, meansbelow said coil to collect water, means to cause a flow of air upwardlythrough said coil and counter to said spray and means defining a flowpath from said water-collecting means to said spraying means,- said flowpath including a passageway through said coil to provide forcountercurrent flow, indirect heat exchange between the fluid to becooled and the water flowing from the water collecting means to thespraying means.

6. Apparatus as claimed in claim 4 further comprising a wet deck sectionin the region of counterflow of air and spray.

7. Apparatus as claimed in claim 5 further comprising'a wet deck sectionin the region of counterflow of air and spray.

References Cited by the Examiner UNITED STATES PATENTS 1,732,963 10/29Burhorn 623 10 2,1 66,158 7/39 Kalischer 625 13 2,257,983 10/41 Shipman623 05 2,787,134 4/57 Boling 62305 CHARLES SUKALO, Primary Examiner.HERBERT L. MARTIN, FREDERICK L. MATTESON,

JR., PERCY L. PATRICK, Examiners.

1. THE METHOD OF IMPROVING THE EFFICIENCY OF EVAPORATIVE HEAT EXTRACTIONTHAT COMPRISES AS THE FIRST STEP IN EXTRACTING HEAT FROM A FLUID THATHAS ABSORBED HEAT, PASSING SAID FLUID TO HAVE HEAT EXTRACTED THEREFROMAND A COOLING LIQUID IN MUTUAL HEAT EXCHANGE RELATION WITHOUTEVAPORATION OF SAID COOLING LIQUID AND THEN PASSING THE SAME FLUID ANDOF ALL SAID LIQUID IN MUTUAL HEAT EXCHANGE RELATION WHILE EVAPORATING ATLEAST A PORTION OF SAID COOLING LIQUID.